You should know what you mean by "solving" the system of linear equations.
Since there are only 2 equations for 4 variables,
the space of solutions is 2-dimensional.
(If there were 2 equations for 2 variables, the solution space would often be 0-dimensional, yielding only one solution.)
In this case, the solution space is parametrized by 2 variables.
Assuming we take z and w for parameters,
you are asked to express (x, y, z, w) in terms of z and w.